The preferred embodiment concerns a toner roller for use in a developer station for a printer or copier with a roller-shaped base body that has an electrically conductive surface on which is arranged an insulation layer. The preferred embodiment also concerns a method to produce a toner roller.
Toner rollers are important structural elements in developer stations for printers or copiers. A typical toner roller is used as an applicator roller that is situated opposite an intermediate carrier, for example a photoconductor roller or a photoconductor belt. During operation the applicator roller carries a homogeneous layer of toner particles. The surface of the intermediate carrier bears a latent charge image corresponding to an image to be printed. As a result of electrical field forces, toner particles are attracted by the surface of the intermediate carrier and are transferred from the applicator roller to this surface (possibly while overcoming an air gap) and arrange themselves corresponding to the latent charge image.
The roller-shaped base body has an electrically conductive surface so that the toner particles can be held on the surface of the toner roller with the aid of electrical voltages. So that voltage flashovers do not occur within the developer station and also towards the intermediate carrier, the toner roller must be provided with an insulation layer. The insulation layer must be sufficiently abrasion-resistant to the developer mixture (comprising toner particles and ferromagnetic carrier particles).
Toner rollers which use a ceramic layer as an insulation layer are known from U.S. Pat. No. 6,327,452 B1 and U.S. Pat. No. 5,473,418. Such ceramic layers have pores that can absorb moisture, which reduces the capability of the toner roller to accept toner particles and in particular to release toner particles.